In the UK, specialist neonatal units that treat a large volume of infants were found to have much greater survival rates than less busy units, a new study published in BMJ Open reports.

Specifically, the research found that the chances of survival were 30% higher for babies born prematurely after 27-32 weeks of pregnancy, and 50% higher for babies born after less than 27 weeks of pregnancy.

Neonatal units were classified as being high-volume if they gave at least 3,480 days of care each year to babies born prematurely after less than 32 weeks of pregnancy.

Previous studies have been carried out that have found that low-volume neonatal units are associated with increased mortality rates. The majority of these studies have been carried out in the US rather than the UK, where the variability in neonatal unit volume is particularly wide.

In the UK in 2003, perinatal centers were reorganized into managed clinical networks (MCNs), providing some of the benefits of a centralized service while allowing smaller, low-volume perinatal centers to remain open to offer services locally.

Emphasis is placed on transferring women with a high risk of delivery at less than 27 weeks gestation to units with a higher care level or high-volume if required.

Since the formation of the MCNs, the number of prematurely born infants in higher care level units has increased significantly, as has the transfer rate between units, although the effect that this change has had on clinical outcomes has remained unclear.

According to the World Health Organization (WHO), an estimated 15 million babies are born prematurely every year. One million of these die annually as a result of preterm birth complications, though three-quarters of them could be saved with current interventions. The US currently has the sixth highest number of preterm births per year worldwide.

An investigation of neonatal care

The researchers aimed to investigate how the designation and volume of neonatal care at the hospital of birth impacted on the survival and health of preterm babies, examining 20,554 babies admitted to 165 British National Health Service hospital neonatal units in England between 2009-2011.

The WHO report that the majority of deaths that occur as a result of preterm birth complications can be prevented.

The units examined participated in the Neonatal Economic, Staffing and Clinical Outcomes Project (NESCOP) and all regularly provide data to the UK's National Neonatal Research Database (NNRD).

Out of the babies examined, 17,955 were born between 27-32 weeks of pregnancy (premature) and 2,559 were born after less than 27 weeks (very premature).

The hospitals contributing data to the study had the following neonatal units:

Level 3 units: a designated specialist unit that receives transfers from other units

Level 2 units: a unit offering high dependency care with some degree of short term intensive care

Level 1 units: a unit without any high dependency or intensive care facilities.

In the study, 27% of the hospitals examined had level 3 units, 49% had level 2 units and 24% had level 1 units.

Of the 20,554 babies born, 1892 (nearly 10%) were born in hospitals with high-volume units that were not level 3. Another 1,817 were born on level 3 units that were not classified as having a high volume.

Increased survival rate

The researchers found that, while there was no difference in survival rates for very premature babies regarding the level of the neonatal unit they were admitted to, there was a difference concerning the volume of the neonatal unit.

They found that babies born prematurely and admitted to high-volume neonatal units were 30% more likely to survive than those born in lower-volume units.

The survival rate increased for very premature babies to 50% if they were admitted to a high-volume unit.

The authors acknowledge that there are limitations to their study. The results do not account for deaths in delivery suites, although the authors state that high-volume delivery suites are associated with reduced mortality rates and are usually found in hospitals with high-volume neonatal units.

The study also did not use any data from the small number of hospitals that do not contribute to either the NNRD or NESCOP and so was not wholly inclusive of the UK's neonatal services.

Finally, the study does not assess the impact of subsequent transfers between medical units, and the authors highlight this as an area of future study.

The researchers say that, overall, their findings regarding the impact that volume has on neonatal outcomes should be "an important consideration for policy makers deciding the optimal organization of neonatal specialist services."

Certainly, this study from BMJ Open offers further insight into how best the problem of preterm births can be approached, and hopefully the benefits of this will not be solely limited to the UK.

Please note: If no author information is provided, the source is cited instead.

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